Thermostatic device and means for mounting same

ABSTRACT

A thermostatic device including a housing containing a bimetallic disc or strip which engages a cruciform-shaped member, the cross arm of which engages a pair of pins which bear against leaf-spring-type movable contact arms while the stem of the cruciform-shaped member can form reset means providing a simple means for resetting the disc. Mans for mounting the thermostatic device include a plate supporting a plurality of springs, each spring in turn urging a housing of the thermostatic device in a direction away form the plate of the device so that when the plate is secured to a surface the temperature of which is to be sensed, the springs urge the thermostatic housing into contact with the surface.

United States Patent [72] Inventors John Pringle [54] THERMOSTATICDEVICE AND MEANS FOR 112, 337, 338, 339, 340, 348, 354, 363, 365, 367,375, 380; ZOO/168C [56] References Cited UNITED STATES PATENTS 3,470,5179/1969 Ohlemacher et a1 337/348 3,164,701 1/1965 Kirchhubel 337/354 X2,538,080 1/1951 Bolesky 337/354 X FOREIGN PATENTS 286,193 8/1965Australia 337/363 Primary Examiner-Bernard A. Gilheany AssistantExaminer-Dewitt M. Morgan Attorneys-Harold Levine, Edward J. Connors,Jr., John A.

Haug, James P. McAndrews and Gerald B. Epstein ABSTRACT: A thermostaticdevice including a housing containing a bimetallic disc or strip whichengages a cruciformshaped member, the cross arm of which engages a pairof pins which bear against leaf-spring-type movable contact arms whilethe stem of the cruciform-shaped member can form reset means providing asimple means for resetting the disc. Mans for mounting the thermostaticdevice include a plate supporting a plurality of springs, each spring inturn urging a housing of the thermostatic device in a direction awayform the plate of the device so that when the plate is secured to asurface the temperature of which is to be sensed. the springs urge thethermostatic housing into contact with the surface PAT-ENTEDSEP28 |97l3509522 sum 2 OF 3 I THERMOSTATIC DEVICE AND MEANS FOR MOUNTING SAMEThis invention relates to an assembly for a thermostat.

In some circumstances there is a need for a double pole single throwthermostat, so that both lines of a device a heater for example, can beisolated from the electrical source. According to one type of prior artthermostat, a bridge member interconnects a pair of transverse bridgemembers which carry contacts thereon cooperable with fixed contacts, thetransverse bridge members being spring loaded by means of helical wiresprings. However, these are subject to certain failings, one of the mainproblems being the difficulty of obtaining a substantially simultaneousbreak of the contacts, so that one contact will tend to pit much morethan the other. A second objection is that the device described isunnecessarily complex, and yet a third objection is that the cost of thecontacts (which are usually of silver or other expensive material) ishigh because of the use of four contacts in a single switch. The instantinvention overcomes the above-noted shortcomings and accordinglycomprises the apparatus hereinafter described, the scope of theinvention being indicated in the following claims.

It is an object of the present invention to provide a two pole singlethrow thermostat having contacts which break simultaneously uponactuation of a thermostatic disc. Another object is the provision of adevice which is relatively inexpensive, easy to assembly and of arelatively simple, uncomplicated nature, yet reliable in operation andeasily calibrated. Yet another object is the provision of a thermostaticassembly comprising a plurality of thermostatic switches each of whichis in firm thermal contact with a surface, the temperature of which isto be sensed.

In the accompanying drawings in which one of the various possibleembodiments of the invention is illustrated,

FIG. 1 is a top plan view of a device made according to the presentinvention with the cover removed;

FIG. 2 is a bottom plan view of the FIG. 1 device with the thermostaticdisc and disc retaining cap removed;

FIG. 3 is a cross-sectional elevation taken on lines 33 of FIG. 1 butincluding the cover, disc and cap;

FIG. 4 is a cross-sectional elevation taken on lines 4-4 of FIG. 3, alsoincluding the cover, disc and cap;

FIG. 5 is a plan view of an assembly showing the thermostatic devicemounted on a support plate;

FIG. 6 is a front elevation of the FIG. 5 assembly;

FIG. 7 is a side elevation of the FIG. 5 assembly; and

FIG. 8 is a plan view of the support plate shown in FIGS. 5-7.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

Turning now to the drawings, and especially FIGS. 5-8, support plate 10is substantially rectangular in form but has a pair of parallel oppositeupturned flanges, 11,12, the plate being provided with a pair ofopenings 14,16, through which is positioned cylindrically shapeddisc-retaining cups 20,20 respectively, of disc-type thermostats. Itwill be understood that more than two openings could be provided if itwere desirable to mount more thermostatic switches. Support plate 10 isprovided with two pairs of apertures rm and bJz for each of thethermostats, each pair of apertures having extending between it a wireor leaf spring 18 which engages an out-turned flange 24 on thedisc-retaining cap 20 of the thermostat. Spring 18 then urges thethermostat disc-retaining cap through the opening so that when thesupport plate 10 is clamped to a surface (not shown) which is to besensed, the disc-retaining caps are urged by the respective springs intocontact with the surface with a pressure which is a function of thedeflection of the springs and can therefore be maintained withinaccurately defined limits. Reference may be had to FIG. 7 wherein flange24 is shown in dotted lines showing the movement possible for suchadjustment. Face 38 of the disc-retaining cap being adjacent to the discconstitutes the sensing medium, and since this will be urged into'contact with the surface the temperature of which is to be sensed byspring means 18 it follows that the disc will tend to occupy a positionwith a minumum air gap. If desired, for even quicker response totemperature changes, an aperture may be provided in face 38 tofacilitate heat transfer from the surface to be sensed to disc 34.

The two switches are interconnected by a small bus bar 26 which in thisembodiment is of L-shape and which is of small thickness so thatdifferential movement can take place between the two housings of the twothermostats. This arrangement then makes possible a simple assemblywherein a single contact single throw thermostat 30 can be used fornormal control of a heating means while the double-contact single-throwout of circuit both lines leading to an element for example. Thedouble-contact thermostat can conveniently be of the type which, havingsnapped open circuit cannot be placed back into circuit except bydepression of a reset button.

The double-contact single-throw thermostat in this embodimentincorporates a number of improvements over previous thermostats. Thisthermostat is a disc-operated thermostat wherein a concave disc 34 isretained in a disc-retaining cap 20 which is of cylindrical form havinga stepped portion 36 near a flat face 38 and adjacent cylindrical walls40 which terminate in flared flange 25 and outwardly extending radialflange 24 at the mouth of the cap. Indexing groove means 55 mayconveniently be provided in flange 25 to facilitate assembly. The discis in contact with the top end 42 of a stem of a cruciform-shaped member44, the bottom end 46 projecting through cover 66 and constituting areset button.

The cross portion 48a, 48b of the cruciform-shaped member 44 engages theupper ends of a pair of matched pins 52a,52b which are freely slidablein respective apertures 54a,54b, the lower ends of the pins engagingleaves of leafspring-type movable contact arms 56a,56b respectively.These arms have on each a contact 57a,57b respectively which engages anddisengages a corresponding fixed contact 58a,58b in housing 50. Themovable distal ends of the arms, however, carry silver or other lowresistance metal contact members 57a, 57b which engage correspondingfixed contact members 58a,58b respectively on the housing, and the twoconductors are broken each by a mating contact as the switch operates.By utilizing the matched pin arrangement it becomes possible to getsubstantially simultaneous opening of the two contacts, and this in turngreatly reduces the damage to contacts. Adjustment is achieved by merelychanging the length of the pins. Alternative adjustment can be made bybending the leaf spring members by biasing overlying terminal members60a,60b respectively mounted in rectangular parallelopiped housing 50.Further, stationary contact members 6la,6lb which mount stationarycontacts 58a, 58b respectively, can be bent to effect desiredcalibration. Similarly, the dimension between the upper end of the sternpart of the cruciform member and the upper ends of the pins can beexactly adjusted by having matched pins which are of length chosen tosuit a particular switch. Cover 66 of electrically insulating materialencloses the switch area.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above apparatus withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

We claim:

1. A two pole thermostatic switch comprising a base of electricallyinsulating material, three generally parallel bores extending through aportion of the base, a slot communicating with the three bores, thebottom wall of the slot forming a stop element, a thermostatic discmounted in the base, cap means received on the base retaining the discin place; primary mo tion transfer means comprising a cruciform-shapedmember having an elongated stem with two opposite ends and a cross armintermediate the two ends, the cross arm having two distal end portions,the cruciform member slidably mounted in the base in the slot with thestem in one of the bores, the stop element limiting movement of thecross arm with one end of the stem engageable with the disc; two movablecontact arms mounted on the base and extending into a switch cavityformed in the base, and movable toward and away from respectivestationary contact arms mounted in the base; two matched supplementarymotion transfer pins slidably mounted in the other two bores in the baseand extending between a respective distal end portion of the cross armand a respective contact arm and adapted to transfer motion from thedisc through the cruciform member to the respective movable contact arm.

2. A switch according to claim 1 in which a cover encloses the switchcavity, a hole is provided in the cover and the other end of theelongated stern of the cruciform extends therethrough to serve as aresetbutton.

3. A switch according to claim 1 in which the switch cavity is formedwithin a portion of the base which is generally a rectangularparallelopiped while the disc is located on a portion of the base whichis generally cylindrical.

4. A switch according to claim 1 in which an elongated terminal memberoverlies and is biased against each movable contact arm and extends intothe switch cavity to permit calibration of each pole by bending thedistal portion of the terminal member to change the bias of the portionagainst the movable contact arm.

1. A two pole thermostatic switch comprising a base of electricallyinsulating material, three generally parallel bores extending through aportion of the base, a slot communicating with the three bores, thebottom wall of the slot forming a stop element, a thermostatic discmounted in the base, cap means received on the base retaining the discin place; primary motion transfer means comprising a cruciform-shapedmember having an elongated stem with two opposite ends and a cross armintermediate the two ends, the cross arm having two distal end portions,the cruciform member slidably mounted in the base in the slot with thestem in one of the bores, the stop element limiting movement of thecross arm with one end of the stem engageable with the disc; two movablecontact arms mounted on the base and extending into a switch cavityformed in the base, and movable toward and away from respectivestationary contact arms mounted in the base; two matched supplementarymotion transfer pins slidably mounted in the other two bores in the baseand extending between a respective distal end portion of the cross armand a respective contact arm and adapted to transfer motion from thedisc through the cruciform member to the respective movable contact arm.2. A switch according to claim 1 in which a cover encloses the switchcavity, a hole is provided in the cover and the other end of theelongated stem of the cruciform extends therethrough to serve as a resetbutton.
 3. A switch according to claim 1 in which the switch cavity isformed within a portion of the base which is generally a rectangularparallelopiped while the disc is located on a portion of the base whichis generally cylindrical.
 4. A switch according to claim 1 in which anelongated terminal member overlies and is biased against each movablecontact arm and extends into the switch cavity to permit calibration ofeach pole by bending the distal portion of the terminal member to changethe bias of the portion against the movable contact arm.